1. Field of the Invention
This invention relates to a permeable membrane. More particularly, this invention relates to a permeable membrane which excels in biocompatibility and enjoys prominent safety.
2. Description of the Prior Art
In the recent medical field, the dialysis of blood represents the segments in which the application of permeable membranes is playing an important role. The patients who have been deprived of normal renal functions and are suffering from renal diseases follow the rule of relying on the dialysis of blood to attain removal of the metabolite and surplus water which would have been excreted normally by their kidneys, keep the electrolyte in the body fluid at a fixed concentration, and maintain the acid-base equilibrium. This is why the dialysis of blood has now come to pass as the pronoun for the so-called artificial kidney. Besides, it has come to function as an important medical technique to be used for the removal of harmful chemicals from the blood of patients intoxicated with a soporific drug or an agricultural pesticide or the removal of renal toxin from patients with renal diseases.
Heretofore, such cellulose type membranes as regenerated cellulose membranes and cellulose acetate membranes have been extensively used for the dialysis of blood in such applications as described above. Through these cellulose type membranes function excellently in the purgation of low molecular substances, they do not deserve to be called fully satisfactory in terms of the purgation of medium to high molecular substances. Moreover, they have a strong possibility of inducing such immunological disorders as activation of a complement and transient leukopenia. Since the cellulose type membranes, on contact with blood, cause coagulation of the blood, they require abundant use of an anticoagulant for the prevention of the coagulation.
Further, for the purpose of eliminating these drawbacks of the cellulose type membranes, permeable membranes made of various synthetic polymers such as, for example, hydrophilic and hydrophobic polymers represented by polyvinyl alcohols, polyacrylonitrile, polysulfones, polymethyl methacrylate, and polyamides have been proposed and developed.
Though most of the permeable membranes made of these synthetic polymers excel those of cellulose type in terms of permeability, the permeable membranes made of hydrophilic polymers fail to acquire sufficient mechanical strength and those made of hydrophobic polymers entail such complexity as to require a treatment for impartation of hydrophilicity in preparation for actual use. The permeable membranes of both the two kinds are short of being fully satisfactory in terms of biocompatibility.
Besides, permeable membranes made of such copolymers as acrylonitrile-sodium methacryl sulfonate copolymer, polycarbonate-polyether block copolymer, and ethylene-vinyl alcohol copolymer which possess a hydrophilic segment and a hydrophobic segment as described in Extra Issue 84 on Chemistry, Biomedical Polymers, Kagaku Dojinsha, pp. 142-145, Handbook on Technique for Use of Membranes, Saiwai Shobo, pp. 663 to 713, and JP-A- 59-193,102(1984), for example are now in the process of development. Though the permeable membranes made of such copolymers possessing a hydrophilic segment and a hydrophobic segment as described above generally exhibit fairly satisfactory characteristics in terms of biocompatibility, they do not deserve to be called fully satisfactory and have room for further improvement in the aspects of safety, thermal stability, and mechanical strength and in such characteristic properties as permeability to water and permeability to other substances which are essentially required to be fulfilled by permeable membranes for blood.
An object of this invention, therefore, is to provide a novel permeable membrane.
Another object of this invention is to provide a permeable membrane which excels in biocompatibility and abounds in safety.